Best ESRGAN API for 4× AI Image Upscaling

A production REST API that upscales any image to 2×, 3×, or 4× resolution using the Real-ESRGAN algorithm. One HTTP POST. PNG output. Under 10 seconds for most images. $0.01 per image — 500 free credits included, no credit card required. The best ESRGAN API for print shops, e-commerce, and stock photo workflows — with SDKs in six languages.

Quick start — one API call to upscale 4×

Sign up, grab your key from the dashboard, and POST your image. The endpoint returns a generation id; poll GET /v1/image/upscale/{id} until status=completed, then download the upscaled PNG from output_url.

curl -X POST https://api.pixelapi.dev/v1/image/upscale \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -F "[email protected]" \
  -F "scale=4"
# Response: {"id": "uuid", "status": "queued", "operation": "upscale", "credits_used": 10.0}

# Poll until completed
curl https://api.pixelapi.dev/v1/image/upscale/UUID \
  -H "Authorization: Bearer YOUR_API_KEY"
# Response: {"generation_id": "uuid", "status": "completed", "output_url": "https://..."}

pip install pixelapi
---
from pixelapi import PixelAPI

client = PixelAPI(api_key="YOUR_API_KEY")
result = client.upscale(image="photo.jpg", scale=4)
result.save("photo_4x.png")  # high-res PNG

# Custom output dimensions
result = client.upscale(
    image="product.jpg",
    target_width=3000,
    target_height=4000,
    fit_mode="pad_white"
)
result.save("product_hi_res.png")

npm install pixelapi
---
import { PixelAPI } from "pixelapi";

const client = new PixelAPI({ apiKey: process.env.PIXELAPI_KEY });
const result = await client.upscale({ image: "./photo.jpg", scale: 4 });
await result.save("photo_4x.png");  // high-res PNG

// Custom dimensions
const sized = await client.upscale({
  image: "./product.jpg",
  targetWidth: 3000,
  targetHeight: 4000,
  fitMode: "pad_white",
});
await sized.save("product_hi_res.png");

composer require pixelapi/pixelapi
---
<?php
use PixelAPI\Client;

$client = new Client(getenv("PIXELAPI_KEY"));
$result = $client->upscale(["image" => "photo.jpg", "scale" => 4]);
file_put_contents("photo_4x.png", $result->getBody());

// Custom dimensions
$result = $client->upscale([
    "image"        => "product.jpg",
    "target_width" => 3000,
    "target_height"=> 4000,
    "fit_mode"     => "pad_white",
]);
file_put_contents("product_hi_res.png", $result->getBody());

gem install pixelapi
---
require "pixelapi"

client = PixelAPI::Client.new(api_key: ENV["PIXELAPI_KEY"])
result = client.upscale(image: "photo.jpg", scale: 4)
File.binwrite("photo_4x.png", result.body)

# Custom dimensions
result = client.upscale(
  image: "product.jpg",
  target_width: 3000,
  target_height: 4000,
  fit_mode: "pad_white"
)
File.binwrite("product_hi_res.png", result.body)

go get github.com/pixelapi/pixelapi-go
---
import "github.com/pixelapi/pixelapi-go"

client := pixelapi.New("YOUR_API_KEY")
result, err := client.Upscale("photo.jpg", pixelapi.UpscaleParams{Scale: 4})
if err != nil { panic(err) }
result.Save("photo_4x.png")

// Custom dimensions
result, err = client.Upscale("product.jpg", pixelapi.UpscaleParams{
    TargetWidth:  3000,
    TargetHeight: 4000,
    FitMode:      "pad_white",
})
result.Save("product_hi_res.png")

Best ESRGAN API pricing — compared to rivals

PixelAPI uses a simple per-image credit model with no subscription lock-in. Compare against the main alternatives:

Pricing verified from each rival's public pricing page May 2026. PixelAPI per-image price is set at exactly half the cheapest rival's verified per-unit rate, per our published pricing policy.

What parameters does the ESRGAN API accept?

What you get back

Combined upscale + face enhancement

For portrait photos, old family photos, or any image with faces, use POST /v1/image/enhance. It chains 4× upscaling with face restoration in a single call — sharper faces, reconstructed fine details, all in one request. Costs 14 credits ($0.014) — cheaper than calling both endpoints separately.

curl -X POST https://api.pixelapi.dev/v1/image/enhance \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -F "[email protected]" \
  -F "scale=4" \
  -F "face_enhance=true"

Common workflows using the ESRGAN API

The ESRGAN Upscale API is the foundation for these production workflows:

Integrations & SDKs

Comparison vs alternatives

Also compare: vs BigJPG · vs Claid.ai · vs Deep Image AI · Topaz Gigapixel open-source alternatives

Rate limits & error handling

Default 60 requests/minute on the free tier, 600 on paid tiers. Exceeding the limit returns HTTP 429 with a Retry-After header. Recommended strategy: exponential backoff starting at 2s, doubling on each retry up to 30s. Both the Python and Node SDKs handle this automatically.

If target dimensions require more than 4× of the (possibly pre-shrunk) input, the API returns HTTP 400 with a message explaining the maximum achievable dimensions. Credits are never deducted for rejected requests.

# Python SDK — automatic 429 retry with backoff
from pixelapi import PixelAPI
client = PixelAPI(api_key="...", max_retries=4)
result = client.upscale(image="batch_photo.jpg", scale=4)  # auto-retries on 429

Frequently asked questions